OST File Cannot be Opened Outlook Error in Windows – Verified Solutions

Updated On - December 13, 2023 by Deepika Singh | Reading Time: 6 minutes

Summary: When it comes to using MS Outlook, one cannot even compromise for a single day. One is so professionally dependent on MS Outlook that errors such as the OST file cannot be opened in MS Outlook can interrupt its functioning to a great extent. Here we will discuss some common methods to fix this error. A professional tool to effortlessly solve this issue will also be discussed.

MS Outlook is a great email client to work on. The number of users dependent on it have been increasing over the period of time. It provides an amazing storage facility to the users in the form of OST and PST files. While the former helps to save the data on the local drive, the latter helps to save the data on the server. These files are synced on a real time basis and store all the information in the mailbox such as emails, contacts, attachments, images, calendars and journals.

However, at times, users are not able to open these OST files in MS Outlook. This is an error and has to be fixed immediately or else you will not have access to your data. In this article, we will share some of the most common methods to fix OST files that cannot be opened in MS Outlook error. But before that, let us know the reasons behind this error.

Reasons behind error

There are various common reasons due to which the OST file cannot be opened in MS Outlook. Here are some of them.

  • The OST file is itself corrupt.
  • The OST file fails to synchronize with the Exchange Server.
  • If the computer shuts down improperly, the OST file fails to open.
  • Continuous interference of Antivirus software.

Methods to Fix OST File Cannot be Opened Outlook Error

Here are some of the common methods that can be of great help to fix this issue.

Method 1: Check connectivity

One must make sure that MS Outlook is connected to the internet. Lack of connection can definitely hinder the OST files from opening.

Method 2: Repair OST file

The inherent corruption of the OST file can be a great reason due to which it cannot open on MS Outlook. Therefore, repairing the file becomes important. Here are the steps that the users can follow for getting the desired results.

  1. Close MS Outlook.
  2. Open the File Explorer and then go to the location where the OST files are saved.
  3. Right-click on the file and then go to properties.
  4. Select the General tab and go to the Advanced option.
  5. In the Advanced Window, uncheck the “Allow files in this folder to have contents indexed in addition to file properties’ ‘ option and click OK.
  6. Now, open the Control Panel and go to Programs and Features.
  7. Right-click on the Microsoft Office installation and select Change.
  8. In the Microsoft Office Setup window, select Repair and click Continue.
  9. Follow the on-screen instructions to repair the OST file.

Method 3: Create a new Profile

A damaged or a corrupt MS Outlook user profile can be a reason due to which the OST file does not open in MS Outlook. Follow the given steps to fix this issue.

  1. Close MS Outlook.
  2. Open the Control Panel and go to Mail. Create a new Outlook Profile to Fix OST File Cannot be Opened Outlook Error
  3. In the Mail Setup window, click on the Show Profiles button.
  4. Click on Add to create a new profile. Step 4
  5. Follow the on-screen instructions to set up the new profile. Step 5
  6. Once the new profile is set up, open Outlook and try opening the OST file in the new profile.

Method 4: Disable faulty Add-ins

Sometimes, the faulty Add-ins can be a great reason due to which OST files do not open in MS Outlook. Here are the steps to disable them.

  1. Go to Start and click on Run.
  2. Enter outlook.exe/safe. This will run MS Outlook in a safe mode. Disable faulty Add-ins to fix this error
  3. Open the File tab and then go to Options and Add-ins. Step 3
  4. In the Outlook Options window, find the Manage section at the bottom. Make sure the COM Add-ins option is selected in the drop-down menu, and then click Go. Step 4
  5. Uncheck the Add-ins and close the application. Step 5
  6. Run MS Outlook in normal mode. This will help you to know which Add-ins are faulty and resisting the OST files from opening.

Method 5: Disable and Enable the Cached Exchange Mode

  1. Close MS Outlook.
  2. Open Control Panel.
  3. Set View by small icons.
  4. Open Mail (Microsoft Outlook). Disable Cached Exchange Mode to resolve this error
  5. In the Mail Setup window, select Email Accounts. Step 5
  6. Under the Email tab, select Exchange account and click Change. Step 6
  7. Uncheck ‘Use Cached Exchange Mode.’ Step 7
  8. Click Next.
  9. Click Finish.
  10. Start MS Outlook again.

Limitations of the Manual Methods

There are multiple limitations of the manual methods.

  • These methods are time consuming and lengthy.
  • They are complicated.
  • Beginners find it difficult to rely on this method.
  • It often results in data loss.

Regain OST Repair Tool: An automatic solution to fixing errors

Now that we know the limitations of the manual methods, it is important to discuss a professional method that will help to fix the OST file that is not opening in MS Outlook error. This Regain OST Repair tool is an automatic tool that easily repairs the damaged and corrupt OST files that are damaged beyond the levels that can be repaired from the manual methods. It comes with an easy interface for beginners. Without compromising the integrity of data, this tool easily repairs the damaged file. It allows the users to preview the repaired file before actually saving it.

One can also convert and export the OST files to multiple formats such as PST, EML, MSG and MBOX in a hassle-free manner. It can repair large-sized OST files also. In fact, it helps to retrieve permanently deleted files as well. It is the best solution that even helps to overcome the limitations of manual methods.

Free Download100% Secure Buy NowPrice: $39

Follow these Steps to Fix this Errors using Regain Software

  • Firstly, download and install Regain OST Recovery tool on your computer.Steps to Repair OST file
  • Secondly, launch the tool and add the corrupt OST file that you want to repair.Step 2
  • Once the scanning process is complete, the tool will display a preview of the recovered data.Step 3
  • Following, select the data that you want to save and click on the Export button.Step 4
  • Choose the format and folder in which you want to save the data.Step 5
  • Lastly, click on the OK button to save the data.


Therefore, one is able to understand that the methods that have been explained above are very accessible and help a user to access the OST files on MS Outlook. Even if the manual methods are not helpful to an extent, Regain OST Repair tool should be the go-to tool that the users must rely on.

Frequently Asked Questions

Ques1. How can the ‘OST File Cannot be Opened in MS Outlook’ error impact daily tasks?
Ans. This error disrupts normal MS Outlook functioning, potentially leading to a loss of access to critical data. The blog provides verified solutions to address and resolve this issue effectively.

Ques2. Why is it essential to fix the “OST File Cannot be Opened” error in MS Outlook?
Ans. MS Outlook is crucial for professional communication, and errors preventing the opening of OST files can disrupt its functionality. This blog provides solutions to resolve this issue.

Ques3. How does the Regain OST Repair tool address the limitations of manual methods?
Ans. The Regain OST Repair tool provides a quicker, more straightforward solution, eliminating the time-consuming and complicated aspects associated with manual methods.

Ques4. Several third-party tools are available in the market, so why should I choose the Regain OST Repair tool?
Ans. Regain OST repair tool is used and trusted by several professionals. Its pocket-friendly price and unmatched features make this tool stand above the competition.


Author: Deepika Singh

My self Deepika Singh working as a Technical Writer in Regain Software. Having 4+ years experience in Writing Technical blogs, Manual Guides and Articles. I am working on all Regain Software products.

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